The invention relates generally to a non-oil-based creping release aid used in the manufacture of tissue and/or towel products. The release aid can be used in conjunction with a creping adhesive aid during the creping process.
In the manufacture of certain wet-laid paper products, such as facial tissue, bathroom tissue, or paper towels, the web is conventionally subjected to a creping process in order to give the web desirable textural characteristics, such as softness, bulk, stretch, and absorbency. The creping process involves the adherence of the web to a rotating creping cylinder, such as an apparatus known as a Yankee dryer, and then dislodging the adhered web from the cylinder with a doctor blade. The impact of the doctor blade against the web ruptures some of the fiber-to-fiber bonds within the web thereby causing the web to wrinkle or pucker.
The severity of this creping action is dependent upon a number of factors, including the degree of adhesion between the web and the surface of the creping cylinder. Greater adhesion causes increased softness, although generally with some loss of strength. In order to increase adhesion, a creping adhesive aid is used to enhance any naturally occurring adhesion that the web may have due to its water content, which will vary widely depending on the extent to which the web has been previously dried. Creping aids should also prevent wear of the dryer surface and provide lubrication between the doctor blade and the dryer surface and reduce chemical corrosion, as well as control the extent of creping. A coating that adheres the sheet just tightly enough to the drum will give a good crepe, imparting absorbency and softness with the least possible loss of paper strength. If adhesion to the dryer drum is too strong, the sheet may pick or even xe2x80x9cplugxe2x80x9d, i.e. slip under the doctor blade, and wrap around the dryer drum. If there is not enough adhesion, the sheet will lift off too easily and undergo too little creping.
The creping adhesive, generally in an aqueous solution or dispersion form, is usually sprayed onto the surface of the creping cylinder, e.g. the Yankee dryer. If the pulp furnish sticks too strongly to the creping cylinder, a release aid is sprayed onto the cylinder. Release aids are typically hydrocarbon oils. These aids assist in the uniform release of the tissue web at the creping blade, and also lubricate and protect the blade from excessive wear. However, the hydrocarbon oil based release aid generally can have a negative effect on the absorbency of the final paper product.
A wide variety of creping adhesives are known to the paper industry. Examples of some adhesives of creping compositions are polyvinyl alcohol, ethylene/vinyl acetate copolymer, animal glue, polyamidoamine-epichlorohydrin resins (PAE resins) and polyvinyl acetate.
U.S. Pat. No. 4,528,316 discloses a creping adhesive aid comprising an aqueous admixture of polyvinyl alcohol and a water-soluble, thermosetting, cationic polyamide resin which provides increased adhesion in the manufacture of creped wadding.
U.S. Pat. No. 5,338,807 discloses a creping adhesive aid comprising the reaction product of a polyamide of a dibasic acid or of the ester of an aliphatic dibasic acid and methyl bis(3-aminopropylamine) with epichlorohydrin in a mole ratio of the polyamide to the epichlorohydrin between about 1:0.1 and about 1:0.33.
U.S. Pat. No. 5,382,323 discloses an improved halogen-free adhesive obtained by reacting adipic acid with diethylenetriamine at equimolar ratios of from 1.2:1.0 to 1.0:1.2 and then crosslinking with a dialdehyde selected from gluteraldehyde, glyoxal, or mixtures thereof. Improved adhesion and full strength are obtained.
U.S. Pat. No. 5,944,954 discloses a creping adhesive comprising cationic starch and optionally a polyvinyl alcohol and a water-soluble thermosetting cationic polyamide-epihalohydrin resin which provides high adhesion and doctorability for dry creping.
Other examples of creping adhesive compositions are disclosed in U.S. Pat. Nos. 5,187,219; 5,246,544; and 5,338,807; and in Canadian Patent No. 979,579. The latter two patents disclose the use of polyamidoamine/epichlorohydrin creping adhesives in conjunction with the aforesaid hydrocarbon oils as a release aid.
As is known to those skilled in the art, both a creping adhesive aid and a creping release aid can be used in the creping process either together in an aqueous solution or separately as aqueous solutions.
Release aids, such as hydrocarbon oils, are petroleum-based. These petroleum-based oils may or may not be used with an emulsifier that maintains the petroleum-based oils in suspension in an aqueous solution for spraying onto the cylinder of the Yankee dryer. As stated herein above, the oil in the final tissue and/or towel paper product can have a negative effect on the absorbency of the final paper product. Due to the hydrophobic nature of the petroleum-based oils, the oil in the final tissue and/or towel paper product can cause a reduction in its absorbency level, i.e. the ability of the final paper product to absorb water or water based solutions.
U.S. Pat. No. 5,660,687 issued to A. J. Allen, et al. discloses a creping release aid for particular use with polyamidoamine/epichlorohydrin creping adhesives. The creping release aid disclosed herein is a plasticizer for the polyamine/epihalohydrin (PAE) resin and has a swelling ratio of at least 0.10 and a solubility parameter greater than 20 MPaxc2xd. This release aid is said to be compatible with and soluble in the PAE type of creping adhesive. Suitable release aids include aliphatic polyols or oligomers thereof having a number average molecular weight of less than 600, polyalkanolamines, aromatic sulfonamides, pyrrolidone, and mixtures thereof. Ethylene glycol is most preferred. Other release aids are propylene glycol, diethylene glycol, glycerol, triethylene glycol, dipropylene glycol, polyalkanolamines, aromatic sulfonamides, pyrrolidone, and mixtures thereof.
There is a need in the industry for an improved creping release aid that is compatible with all types of creping adhesive aids, including the PAE type of adhesive, and that provides a high level of absorbency compared to typical present day oil-based release components while still providing a high degree of lubrication between the paper web and the doctor blade in the creping process.
The invention provides an improved creping release aid comprised of a non-oil-based chemical compound. Preferably, this non-oil-based chemical compound used as a release aid in a creping process is represented by the following formula for its block version:
Rxe2x80x94(OC3H6)y(OC2H4)zOH;
where R is a C8 to C20 alkyl or alkylaryl group, y plus z is greater than 20, and y is greater than z. The y moles of propylene oxide (OC3H6) and the z moles of ethylene oxide (OC2H4) may be added in random or block fashion. As indicated, the block version is depicted in the above formula. The non-oil-based chemical compound generally may be selected from the group consisting of alkoxylated alkylphenols, alkoxylated fatty acids, and alkoxylated alcohols.
In a preferred embodiment, the non-oil-based chemical compound of the invention used as a release aid is an alkoxylated tall oil fatty acid where R is consistent with the alkyl chains of tall oil fatty acid, y is greater than 40, and z is less than 8, with the propylene oxide and the ethylene oxide added in block fashion as represented in the above formula. A further preferred embodiment is when the propylene oxide and the ethylene oxide are added in random fashion.
The release aid of the invention may be used with one or more surfactants in order to help emulsify the major component in the aqueous solution for spraying onto the Yankee dryer. These emulsifiers may include but are not limited to fatty acids, PEG (polyethylene glycol) esters, alkoxylated alcohols, alkoxylated fatty acids, and/or alkoxylated alkylphenols.
The release aid may comprise from about 0% to about 10% water by weight, about 0% to about 20% of one or more emulsifying surfactants by weight, and about 70% to about 100% by weight of the release aid of the above described chemical compound. More preferably, the release aid may comprise 0% water by weight, about 2% to about 10% by weight of one or more emulsifying surfactants, and about 90% to about 98% by weight of the release aid of the above described chemical compound.
If the release aid of the invention is in aqueous form then the aqueous solution comprises from about 90.0% to about 99.99% by weight water and from about 10.0% to about 0.01% solids by weight which comprises the release aid.
The release aid may also be used in combination with a creping adhesive aid that may be of any type that is known to the industry.
The invention further provides a process for creping tissue paper in the manufacture of a paper product, comprising:
a) applying to a rotating creping cylinder an aqueous solution comprising from about 90.0% to about 99.99% water by weight and from about 10.0% to about 0.01% solids by weight comprised of a release aid;
b) pressing a paper web against the creping cylinder to effect adhesion and thereafter release of the web from the surface of the cylinder; and
c) dislodging the web from the creping cylinder with a doctor blade, wherein said release aid in step (a) is comprised of a non-oil based chemical compound represented by the following formula for its block version:
Rxe2x80x94(OC3H6)y(OC2H4)zOH;
where R is a C8 to C20 alkyl or alkylaryl group, y plus z is greater than 20, y is greater than z, and wherein the y moles of propylene oxide(OC3H6) and the z moles of ethylene oxide (OC2H4) may be added in random or block fashion.
Examples of the non-oil-based chemical compound used in the invention are alkoxylated alkylphenols, alkoxylated fatty acids, and alkoxylated alcohols.
The tissue web can be comprised of various types of natural fibers including wood pulps of chemical and mechanical types. The tissue web can also be comprised of particulate fillers, such as kaolin clay, titanium dioxide, and/or calcium carbonate.
It is therefore, an objective of the present invention to provide a release aid in a creping process for the manufacture of a tissue/towel product that is compatible with all types of creping adhesives, that provides lubrication between the paper web and the doctor blade and that allows the amount of adhesion between the paper web and the Yankee dryer to be moderated.
It is still a further objective of the present invention to provide a non-oil-based release aid for a creping process in the manufacture of a tissue/towel product that produces a positive effect on absorbency when compared to typical oil-based release aids.
These and other objectives of the present invention will be better appreciated and understood by those skilled in the art from the following description of the drawings and the claims.